1. Field of the Invention
The present invention is directed to a medical patch and, in particular, an improved transdermal medical patch for providing a treatment therapy such as electrical stimulation and/or delivery of a pharmacological agent such as pain medication, drugs, and hormones.
2. Description of Related Art
Nerves are part of the peripheral nervous system of a human body. They convey sensory signals back and forth from the skin and body organs to the central nervous system. Nerves may become damaged due to wear and tear, physical injuries, infection, and/or the failure of the blood vessels surrounding the nerves. These functional defects may be accompanied by pain, numbness, weakness and in some cases, paralysis. Other problems resulting from damaged nerves may include urinary and fecal incontinence.
Different approaches have been developed to treat the above-mentioned problems. For example, treating urinary incontinence may involve behavior modification such as urinating more frequently and wearing protective undergarments. In certain social situations, however, individuals may not be able to follow the practice of frequent urination or wearing protective undergarments. Another approach involves a medical therapy including taking prescribed drugs. However, this methodology may result in adverse side effects or drug interactions that will ultimately require discontinuation.
Still another technique for treating the above-noted conditions involves stimulation using an electro-medical device that is positioned near a target nerve. One such electro-medical device is commonly referred to as an Implantable Pulse Generator (IPG), which typically includes one or more electrodes, an electrical pulse generator and a power source (e.g., internal and/or external to the body). The electrical pulse generator generates an electrical signal adapted to stimulate a target nerve. When the electrodes receive the signal from the generator, they draw energy from the power source and generate an electric field of suitable strength to stimulate the target nerve.
Implantable Pulse Generators are somewhat effective for stimulating nerves; however, such devices are extremely invasive since they are implanted inside a patient's body during a surgical procedure. Furthermore, IPG's consume a significant amount of power, which may be due to an increase in electrical impedance between the electrodes, or an increase in electrical impedance between the electrodes and the IPG. Increased power consumption may also be caused by a phenomenon referred to as “desensitization of stimulus,” whereby the human body responds to an applied external charge by offering a resistance to the applied external charge. The body resists the applied external charge by increasing the stimulation threshold for a target nerve, thereby rendering the earlier stimulus level ineffective. To overcome this problem, a more powerful charge must be generated, which consumes even more battery power and requires frequent replacement and/or recharging of the batteries.
With some nerve stimulation devices, it has been observed that the generated electric field spreads widely, undesirably affecting untargeted muscles and nerves along with the target nerve. The wide spreading of the electric field significantly reduces the strength of the electrical signal at the target nerve. In order to properly stimulate the target nerve, the strength of the electrical signal must be substantially increased, which requires the device to draw more power from the battery thereby consuming greater energy.
In view of the aforementioned drawbacks, efforts have been sought to stimulate nerves in a more efficacious and non-invasive manner. For example, non-invasive selective nerve stimulation (SNS) medical patches are disclosed in commonly assigned U.S. Patent Publication Nos.: 2005/0277998, filed Jun. 7, 2005 and 2006/0195153, filed Jan. 31, 2006, the disclosures of which are each hereby incorporated by reference in their entirety herein. Specifically, in one or more embodiments thereof, these publications teach a non-invasive, transcutaneous neurostimulation patch that generates and transmits a controlled, amplitude-modulated waveform comprising a carrier signal and a pulse envelope. The carrier waveform is designed to be of sufficient frequency to overcome attenuation due to tissue impedances. The pulse envelope contains specific pulse width, amplitude and shape information designed to stimulate specific nerves.
Medical patches are often adhered to a patient's skin with an active or operating portion of the patch directed toward a target location (e.g., one or more targeted nerves) on the patient. Such medical patches are disclosed in commonly assigned U.S. Patent Publication Nos. 2009/0132018, filed on Nov. 16, 2007 and 2011/0152987, filed on Dec. 18, 2009, the disclosures of which are each hereby incorporated by reference in their entirety herein. The medical patch produces electrical signals and/or delivers a pharmacological agent for achieving a therapeutic benefit to a target site of the body. In some instances, a series of medical patches are sequentially in time applied to the patient, whereby a first medical patch applied by a medical professional is removed from a patient's skin and replaced with a second medical patch. After the passage of time, the second medical patch is removed and replaced by a third medical patch, and so on. Rather than being administered by a physician, nurse or technician, application of the second and subsequent medical patches to the body is often conducted by the patient himself/herself at home. Due to inexperience, replacement medical patches may be improperly aligned over the target site on the patient, e.g. a particular nerve that is the target for nerve stimulation, resulting in less effective treatment therapy. Thus, there is a need to develop a medical patch that may be properly positioned on the body by the patient himself/herself unassisted. The use a separate mechanical placement tool to properly position the medical patch on the body, although permitting self-placement, disadvantageously increases the overall cost and complexity of use while being susceptible to becoming lost or misplaced. All of these concerns may reduce usage of the medical patch thereby limiting the efficacy of treatment therapy.
Once again the lack of experience by the patient in self-positioning the medical patch on the body himself/herself increases the probability of its improper placement on the target site of the body. Such improper positioning of the medical patch may be readily observed visually once it has been adhered to the body. The occurrence of misplacement of the medical patch is particularly significant until the patient becomes more familiar with how to properly position the patch on the body over the target site. In anticipation of such learning curve by the patient, it would be desirable to temporarily adhere the medical patch to the body and visually confirm if it has been properly positioned at the target site. If not correctly located on the body, it would be advantageous to allow the medical patch to be removed and repositioned correctly on the body without having to use a new patch.
With the introduction of small electronic component circuitry today, transcutaneous medical patches typically include electronic circuitry that may, over time, cause skin irritation, redness or lesions. This is of particular concern when the same medical patch remains adhered at the same location on the body for an extended period of time, for example, several days or more. It would therefore be desirable to reduce the occurrence of skin irritation thereby increasing the duration of time over which the medical patch may remain adhered to the same location on the body.
In view of the foregoing, there is a need for medical patch that overcomes the aforementioned problems associated with convention transdermal patches.